Taking that a step further, the common use of detection dogs by police has led to courts' acceptance of an indication by a police dog as probable cause for a search. In other words, if the cops bring out a dog that is trained to detect drugs, human remains, explosives or whatever, and that dog indicates on your backpack, you will almost certainly be denied your Fourth Amendment protection. The cops will search your backpack whether you want them to or not, and the courts will uphold it. But how reliable is the dog, really? Radley Balko, in "The Mind of a Police Dog", says this:
"The Economist's "Babbage" blog summarizes a recent study led by Lisa Lit, a neurologist (and former dog handler) at the University of California-Davis, that demonstrates the startling consequences of that confusion:
[Researchers] asked 18 professional dog handlers and their mutts to complete two sets of four brief searches. Thirteen of those who participated worked in drug detection, three in explosives detection, and two worked in both. The dogs had been trained to use one of two signals to indicate to their handlers that they had detected something. Some would bark, others would sit.The results? Dog/handler teams correctly completed a search with no alerts in just 21 of the 144 walk-throughs. The other 123 searches produced an astounding 225 alerts, every one of them false. Even more interesting, the search points designed to trick the handlers (marked by the red slips of paper) were about twice as likely to trigger false alerts as the search points designed to trick the dogs (by luring them with sausages)."
The experimental searches took places in the rooms of a church, and each team of dog and human had five minutes allocated to each of the eight searches. Before the searches, the handlers were informed that some of the search areas might contain up to three target scents, and also that in two cases those scents would be marked by pieces of red paper.
What the handlers were not told was that two of the targets contained decoy scents, in the form of unwrapped, hidden sausages, to encourage the dogs' interest in a false location. Moreover, none of the search areas contained the scents of either drugs or explosives. Any "detections" made by the teams thus had to be false. Recorders, who were blind to the study, noted where handlers indicated that their dogs had raised alerts.
So here is the question: does a right really exist when agents of the government have such a tool to bypass that right? That is one of those polarizing questions where communitarians will claim that the safety of the "rest of us" trumps the right of that one suspect individual in that one case (with the inference that he is probably guilty anyway); while proponents of individual liberty will point out that if a right can be denied to one individual, it can be denied to any individual.